There are many types of ice cream products on the market including related products such as for example milk ice, sorbet, sherbet and water ice. A typical process for making ice cream products involves some general steps:
Pre-heating and mixing: the liquid ice cream ingredients are heated and blended in a tank and the dry ingredients are added via a mixing unit. A homogenous so called “ice cream mix” (also known just as “mix”) is formed.
Homogenisation, pasteurization, cooling: The ice cream mix is pre-heated in a plate heat exchanger, homogenisated and returned to the plate heat exchanger for pasteurization. The pasteurised ice cream mix is then cooled.
Ageing: The ice cream mix is aged a period of time (typically at least 4 hours) at a temperature of 2-5° C. and during gentle agitation.
Continuous freezing: After ageing the ice cream mix is fed to a continuous freezer in which a controlled amount of air is whipped into the mix and in which a part of the water content of the mix is freezed into small ice crystals. The temperature of the frozen ice cream is typically in the range of −3 to −7° C.
Filling, extrusion, moulding: The frozen ice cream is fed to either filling lines, moulded stick novelty lines or extrusion lines depending on the type of ice cream product to be manufactured. Optionally, the ice cream is first fed via an ingredient feeder for addition of for example nuts, chocolate, jam or fruit pieces.
Continuous hardening: The ready ice cream product is made to harden to a temperature of about −20° C.
In the freezing step it is well-known to use so-called through-flow freezers comprising a freezing cylinder in which a mixture of ice cream mix and air is frozen to ice cream by cooling the freezing cylinder from its outside using a liquid coolant. The ice cream mass is typically transported through the freezing cylinder by pumping. A freezer of this type is described in the international publication WO2013/023986. The document further describes a process for initiating production, i.e. a pre-production step or start-up step, in which the ratio air/ice cream mix is balanced to reach preset values before the frozen ice cream is pumped out of the freezer and to the filling lines. The process described in WO2013/023986 has as its purpose to reduce the time consumed and the amount of waste ice cream produced until stable conditions for the continuous production have been reached.
Another issue during start up, causing waste ice cream, is the temperature of the piping system. The piping system typically comprises from a few meters to a few dozen meters of stainless steel pipes, which pipes transport the frozen ice cream from the freezer to the output nozzles of the filling lines, moulded stick novelty lines or extrusion lines. Before continuous production can be performed the piping system needs to be cooled. Typically, the cooling is made by the ice-cream itself during the transport, i.e. through thermal conductivity between the ice cream and the pipes. Any ice-cream used for the initial cooling is wasted, i.e. all ice cream being fed through the pipes until the pipes have reached a pre-defined low temperature is supplied, via the filling nozzles, to a waste vessel.